Ive put in an enhancement request for configurable heap space in the OBM customization portal, with an increasing number of instances of needing more heap space there is still no way to set this without manually editing the files, the 128 / 768 figure is just laughable these days. bumping up the heap space puts a considerable performance increase for delta generation, and restore speeds.

Even if you replace the files in the customization portal to ones with increased figures, the installer build process emits these files from the build.